This invention relates to intravenous (I.V.) catheter assemblies and, in particular, to a catheter assembly having a cannula tip guard which automatically covers the cannula tip after use to prevent accidental injury from used cannulas.
Intravenous catheters for the infusion of fluids into the peripheral veins of a patient are one the most common devices used in I.V. therapy. In one type of catheter known as an over-the-needle catheter, the cannula and concentric outer catheter are inserted into the vein and the cannula is withdrawn through the emplaced catheter.
A typical over-the-needle I.V. catheter requires the user to remove and then dispose of a contaminated cannula after the cannula tip and catheter are properly located in the vein of the patient. Once the cannula is withdrawn from the catheter, the user's immediate priorities are infusion set connection and site preparation, including the taping of the catheter to the patient. Because of the urgency of these procedures the cannula is normally just dropped conveniently nearby and then retrieved later. Since the cannula at this time is exposed and located close to where the user is completing work with the catheter, accidental self-inflicted injuries are not uncommon. For reasons of the desirability of protecting the user from exposure to hepatitis and AIDS, there is an increasing need to protect the user from accidental cannula injury.
A catheter design which is directed toward this need is shown in U.S. Pat. No. 4,762,516. The catheter shown in this patent includes an elongate body which houses a sliding needle guard. As the needle is withdrawn from the emplaced catheter, the user pushes the tab at the distal end of the needle guard, thereby sliding the needle guard out of the housing and along the needle, until the distal end of the guard covers the needle tip and the proximal end of the guard locks in the housing. The needle and guard may then be set aside with the needle tip fully protected.
Another needle guard is shown in U.S. Pat. No. 5,084,023. The needle guard in this patent includes a sleeve having a locking ring to secure the guard to a return valve assembly. The guard also includes a notch that engages a corresponding recess is the needle to prevent the needle from being withdrawn from the guard.
U.S. Pat. No. 4,834,718 also discloses a needle tip guard. A hub portion of the guard of this patent mounts within the catheter hub and includes a resilient tongue. The tongue flexes outward to engage a recess in the catheter hub when the needle is inserted through the guard. When the needle is withdrawn into the guard, the tongue flexes inward releasing the guard from the hub. The guard is further comprised of a housing that extends the entire length of the blood chamber. A latching mechanism on the extreme end of the housing holds the needle tip within the guard.
While the arrangements described in the above prior art patents provide protection against accidental needle injury, the requirements of each of these devices necessarily requires rather long and/or bulky assemblies. Moreover, the arrangements are somewhat cumbersome to operate for users with small hands and fingers.
Accordingly, it would be desirable for a needle to be securely protected by a small needle guard, and it would be most preferable for the needle guard to be moved into position over the needle tip automatically upon withdrawal of the needle from the patient, without the intervention of any special motion by the user.